The present invention relates to a method and apparatus for shaping cans, such as metal cans used for beverages. More specifically, the present invention relates to a method and apparatus for shaping cans utilizing an inflatable mandrel within the can body in conjunction with various external shaping tools.
Currently, most large-scale mass-produced cans used for food and beverage are straight-wall. Shaped cans can be an important marketing instrument, if means of producing these inexpensively can be established, because they create product identity.
Technology exists for shaping cans, but each available solution has some/all of the following disadvantages:
A relatively high cost because of an inability to decorate the straight-wall can before shaping (because of use of external chucks), and/or complex/high-maintenance means of applying pressure to the can side-wall, and/or capital-intensive means of picking-up/centering the can, and/or the necessity to make can-shaping an additional, separate process.
A reliance on outward-shaping (i.e. expanding the metal in such a way as to increase the straight-wall can diameter in the areas shaped). Particularly in the case of two-piece drawn cans, the scope of this outward-expansion is limited, because current technology already draws the metal to its ultimate degree in order to reduce cost. When the can walls are expanded further for the purpose of shaping, the metal cracks or deforms.
A limitation in shaping scope. This limitation includes inability to shape the entire straight-wall can surface (typically, because the can is held in an external chuck and shaping behind the chuck is not possible), and/or the inability to produce non-radial shapes, and/or the inability to produce outward-expanded as well as inward-compressed shapes.
A limitation to three-piece cans and not usable for two-piece cans.
A limitation in choice of can material (aluminum or steel), typically because expansion requires very high pressures with steel, or because the use of external chucks is unsuitable for thin-walled aluminum cans.